Re: [RFC/PATCH] Disallow commands from within unpopulated submodules.

From: Jeff King <peff@peff.net>
Date: Jan 20, 2017, 21:48 UTC
Message-ID: <20170120214812.hhyjj3ldhhbrohlw@sigill.intra.peff.net>
In-Reply-To: <xmqq37gdxvbx.fsf@gitster.mtv.corp.google.com>

On Fri, Jan 20, 2017 at 01:41:54PM -0800, Junio C Hamano wrote:

Show 12 quoted lines

> Jeff King <peff@peff.net> writes:
> 
> >> And in my current understanding of submodules the check in
> >> .gitmodules ought to be enough, too.
> >
> > Yeah, that probably makes sense. You can have a gitlink without a
> > .gitmodules file, but I don't quite know what that would mean in terms
> > of submodules (I guess it's not a submodule but "something else").
> 
> That may be a lot better than reading the index unconditionally, but
> I'd rather not to see "git rev-parse" read ".gitmodules" at all.  It
> would discourage scripted use of Git for no good reason.

Why is that? Just because it makes rev-parse seem more bloated?

I think Stefan's putting it into git.c is confusing the issue a bit. This is fundamentally about figuring out which git repository we're in, and that procedure is the right place to put the check.

IOW, when we call setup_git_repository() we are already walking up the tree and looking at .git/HEAD, .git/config, etc to see if we are in a valid git repository. It doesn't seem unreasonable to me to make this part of that check. I.e.:

  - if we we walked up from the working tree (so we have a non-NULL
    prefix); and

  - if there is a .gitmodules file; and

  - if the .gitmodules file shows that we were inside what _should_ have
    been a submodule; then

  - complain and do not accept the outer repository as a valid repo.

That adds only an extra failed open() for people who do not use submodules, and an extra config-file parse for people who do. And then only when they are not in the top-level of the working tree (so scripts, etc that cd_to_toplevel wouldn't pay per-invocation).

-Peff